My 1988 LFX F40 build. (Page 28/67)
Daryl M FEB 18, 03:34 AM
So, as I understand it, the published hp & torque for engines are as installed in the car . a Camaro has a much different air box and exhaust than an Impala, or any other less sporty car. Could the biggest factor determining the added Camaro power be air box and exhaust, both of which are designed on the non-sporty models to be very quiet? If that is the case, a high flow cold air intake and less restrictive exhaust may just make more difference than you think.
ericjon262 FEB 24, 09:37 PM

quote
Originally posted by ChuckR:


Could you not port/ polish the heads on the LFX to gain better in and out flow? I know there would be more polishing done on the exhaust side than on a normal head. I have never seen the inside on the LFX heads just spit balling ideas of gaining power on better breathing.




there's alot more that goes into building an exhaust than just flowrate, harmonics play a significant role, and with a integrated manifold like the LFX, you're pretty much stuck with what the factory gives you in the respect.

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Will FEB 25, 10:41 AM

quote
Originally posted by ericjon262:

there's alot more that goes into building an exhaust than just flowrate, harmonics play a significant role, and with a integrated manifold like the LFX, you're pretty much stuck with what the factory gives you in the respect.




Right. Well built long tube headers will do a lot more for an LLT's naturally aspirated power output than any single-pipe exhaust will do for an LFX's naturally aspirated power output.
Daryl M FEB 25, 08:20 PM
It is my understanding that the goal of exhaust design is to equally space exhaust pulses from each cylinder into the collector to encourage scavenging. The common plenum on each head is not ideal for this, but the fact that the firing order alternates banked with each pulse, it isn't as bad as it could be. I would be curious just how big the individual ports make. My guess is that those GM motor engineers have probably considered all of the factors when they did the redesign of the heads for the high feature engine.
Will FEB 26, 12:54 PM
They were designing the engine as a concerted system for the 320-330 HP output range that the LFX and LGX have stock. Look at all the little incrememental changes that happen to move from the 320 HP LFX to the 330 HP LGX...

Now think about what has to happen to build a 400 HP LLT...
La fiera FEB 26, 07:16 PM

quote
Originally posted by Daryl M:
GM motor engineers have probably considered all of the factors when they did the redesign of the heads for the high feature engine.



The only factor they consider is packaging and where to save a buck. Performance is the least of their concerns.
Like you mentioned before that head design is not ideal because of that same reason, make the cheapest design and get it out of the door.
Daryl M FEB 26, 07:53 PM
Will, the big reason the LFX-LGX is at the power level it is has more to do with drivability than money. Yes they are capable of more hp, but at what cost? Longevity, reliability and drivability are more important to GM than saving $10 bucks per car or making a motor that is less reliable and has a narrow power band.
Just my opinion.
Daryl
Will FEB 27, 07:25 AM

quote
Originally posted by Daryl M:

Will, the big reason the LFX-LGX is at the power level it is has more to do with drivability than money. Yes they are capable of more hp, but at what cost? Longevity, reliability and drivability are more important to GM than saving $10 bucks per car or making a motor that is less reliable and has a narrow power band.
Just my opinion.
Daryl



Emissions requirements drive far more than that. The engine would probably be fine at a higher power level in terms of reliability, but wouldn't satisfy emissions requirements. With high compression, DI and VVT, the width of the power band is less of a concern.
Daryl M FEB 27, 04:56 PM
Will, I did a quick search to find the most powerful naturally aspirated automotive v6 under 4 liters. The best I could find was the 4 liter Porche. When adjusted for displacement, it is about 10% more powerful than the LGX. Since the Porche is a performance car and buyers expect different things from it than someone that buys an Impala, 10% doesn't seem like a big deal. I still would be interested to know just how much difference the exhaust, LLT vs LFX really makes.
Will FEB 27, 06:16 PM
You didn't look up the GT3 RS version then...

It may have been on a defunct forum, but I read a build thread of a guy who put a BMW S38 into an E30. He did a blueprinted build and installed an aftermarket intake cam... I don't remember what the wheel number was, but it was enough to estimate crankshaft power at ~390 from a 3.6 liter inline six.